The present invention relates to a hydraulic oil recovery/reutilization system which accumulates a high pressure fluid by an energy of a pressurized fluid returned from a hydraulic actuator in a construction machine, such as a power shovel or the like and re-uses an accumulated high pressure fluid as an actuation energy of an actuator.
As a power shovel, there has been known one, in which an upper pivotal body is provided on a lower vehicular body having a traveling body, for pivotal motion by a pivoting hydraulic motor, a boom is mounted on the upper pivotal body for vertical rocking motion by means of a boom cylinder, an arm is mounted on the boom for vertical rocking motion by means of an arm cylinder, and a bucket is mounted on the arm for vertical swing motion by means of a bucket cylinder.
The foregoing pivoting hydraulic motor, the boom cylinder, the arm cylinder and the bucket cylinder are actuated by supplying a discharged pressurized fluid of a hydraulic pump to one chamber and draining the pressurized fluid of another chamber to a tank, by switching direction switching valves.
For example, the discharged pressurized fluid of the hydraulic pump is supplied to an expansion chamber of the boom cylinder by the direction switching valve for the boom, and in conjunction therewith, the pressurized fluid in a compression chamber is drained for actuating the boom cylinder for expansion, and the discharged pressurized fluid of the hydraulic pump is supplied to the compression chamber of the boom cylinder, and in conjunction therewith, the pressurized fluid in the expansion chamber is drained for actuating the boom cylinder for compression.
As set forth above, since the pressurized fluid returned from the pivoting hydraulic motor, the boom cylinder, the arm cylinder and the bucket cylinder is drained to the tank, an energy of the returning pressurized fluid cannot be used.
For example, in the case of a compression operation of the boom cylinder, a pressure is generated in the pressurized fluid returned from the expansion chamber due to the weight of the boom, the arm and the bucket. However, since the returning pressurized fluid is drained to the tank, the pressure (energy) of the returning pressurized fluid cannot be re-used. On the other hand, there has been proposed an apparatus for recovering and re-using the energy of the returning pressurized fluid of the hydraulic actuator. For example, there has been known a pressurized fluid recovering/reutilization system disclosed in Japanese Examined Patent Publication No. Heisei 3-33922.
As shown in FIG. 1, the pressurized fluid recovering/reutilization system is constructed by connecting a chamber 2 of a single action cylinder 1 as an actuator to a port 4 of a first pump motor 3, connecting a port 6 of a second pump motor 5 mechanically coupled with the first pump motor 3 to a pressurized fluid supply circuit 7, connecting the pressurized fluid supply circuit 7 to the hydraulic pressure source via a check valve 8 and to a pressure accumulator 9. With this system, by supplying a pressurized fluid of the hydraulic pressure source to the pressurized fluid supply circuit 7, the second pump motor 5 performs motoring operation to drive the first pump motor 3. Then, the first pump motor 3 performing pumping operation to supply the pressurized fluid to the chamber 2 of the single action cylinder 1 to actuate the single action cylinder 1 for expansion.
When supply of the pressurized fluid to the pressurized fluid supply circuit 7 is terminated, the single action cylinder 1 is actuated for compression by an external load to generate a pressure in the returning pressurized fluid of the chamber 2 to drive the first pump motor 3 for motoring operation.
By this, the second pump motor 5 performs a pumping operation to generate a high pressure fluid to the pressurized fluid supply circuit 7. The flow of the high pressure fluid is blocked by the check valve 8 and the pressure is accumulated in the pressure accumulator 9.
Then, when the single action cylinder 1 is operated again for expansion by supplying the pressurized fluid to the pressurized fluid supply circuit 7, the high pressure fluid accumulated in the pressure accumulator 9 drives the second pump motor 5. Thus, the first pump motor 3 performs pumping operation to supply high pressure fluid to the chamber 2 to enable re-using of the pressurized fluid (energy) accumulated in the pressure accumulator 9.
The foregoing system accumulates high pressure fluid by energy of the returning pressurized fluid of the chamber 2 of the single action cylinder 1 to supply the pressurized fluid to the chamber 2 of the single action cylinder 1 by the accumulated high pressure fluid again. Thus, the accumulated high pressure fluid is re-used only for the single action cylinder and cannot be re-used for other actuators.
Therefore, an object of the present invention is to provide a pressurized fluid recovering and reutilization system which can solve the problem set forth above.
The first invention is a pressurized fluid recovery/reutilization system characterized by supplying a pressurized fluid of high pressure to a hydraulic pressure source by operating a pressure converter 18 constructed with a first pump motor 16 and a second pump motor 17 which are mechanically coupled by an energy of a pressurized fluid returned from an actuator actuated by the pressurized fluid of the hydraulic power source.
By the first invention, since the pressurized fluid of high pressure is supplied to the hydraulic pressure source by the energy of the returning pressurized fluid of the actuator, the recovered returning pressurized fluid of the actuator can be reused for actuation of another actuator.
The second invention is a pressurized fluid recovery/reutilization system which comprises a primary hydraulic pump 10 supplying a pressurized fluid returned from an actuator, a first circuit 22 supplied the returning pressurized fluid from the actuator, a first pump motor 16 connected to said first circuit 22, a variable displacement type second pump motor 17 mechanically coupled with said first pump motor 16 and connected to a second circuit 25, a third circuit 29 communicating said first circuit 22 and a discharge passage 11 of said primary hydraulic pump 10, a pressure accumulator 27 provided in said second circuit 25, and a reproduction valve 30 switching said third circuit between a state permitting the flow of a pressurized fluid and a state blocking the flow.
By second invention, by switching the flow of the pressurized fluid in the third circuit is switched into blocking state by the reproduction valve 30, the first pump motor 16 is operated for motoring operation by the returning pressurized fluid to cause pumping operation of the second pump motor 17. Thus, the pressurized fluid of high pressure can be accumulated in the pressure accumulator 27.
By switching the third circuit 29 to permit the flow of the pressurized fluid by the reproduction valve 30, the second pump motor 17 is operated to perform motoring operation by the accumulated pressurized fluid of high pressure to cause pumping operation of the first pump motor 16 to supply the discharge passage 11 of the primary hydraulic pump 10 via the third circuit 29 by discharging fluid to the first circuit 22.
By this, the energy of the returning pressurized fluid of the actuator can be reused for actuation of another actuator.
On the other hand, when the second pump motor 17 performs motoring operation, an output torque of the second pump motor 17, namely a torque for driving the first pump motor 16, is varied by increasing and decreasing of the displacement of the second pump motor 17. Thus, by pumping operation of the first pump motor 16, the pressure in the first circuit 22 can be increased and decreased.
By this, the pressure of the first circuit 22 is set to be equal to the pressure of the discharge passage 11 of the primary hydraulic pump 10 or slightly higher than the latter, the pressure in the first circuit 22 can be supplied to the discharge passage 11 of the primary hydraulic pump 10 and reused.
The third invention is a pressurized fluid recovery/reutilization system in which a pressure accumulation valve 26 is provided for establishing and blocking communication of said second circuit 25, and a sequence valve 28 is provided between said second circuit 25 on the side of said second pump motor 17 of said pressure accumulation valve 26 and the discharge passage 11 of the primary hydraulic pump 10.
By the third invention, if the second circuit 25 is blocked by the pressure accumulation valve 26 in the condition where accumulation of the pressurized fluid of high pressure in the pressure accumulator is completed, leakage of the pressurized fluid of high pressure accumulated in the pressure accumulator 27 can be prevented.
On the other hand, when the pressurized fluid of high pressure is fully accumulated in the pressure accumulator 27, since the pressurized fluid of high pressure of the second circuit 25 is supplied from the sequence valve 28 to the primary hydraulic pump 10, the displacement of the pressure accumulator 27 can be made small.
On the other hand, by closing the pressure accumulation valve 26 while the pressure is accumulated by pumping operation of the second pump motor 17, the pressurized fluid of high pressure discharged from the second pump motor 17 is directly supplied to the discharge passage 11 of the primary hydraulic pump 10 from the sequence valve 28.
By this, the energy of the recovered returning pressurized fluid can be reused immediately.
The fourth invention is a pressurized fluid recovery/reutilization system which comprises a primary hydraulic pump 10 supplying a pressurized fluid returned from an actuator, a first circuit 22 supplied the returning pressurized fluid from the actuator, a recovery valve 23 for switching said first circuit 22 between a first state permitting the flow of the pressurized fluid and a second state blocking the flow, a pressure converter 18 having a first pump motor 16 connected to said first circuit 22, a variable displacement type second pump motor 17 mechanically coupled with said first pump motor 16 and connected to a second circuit 25, a third circuit 29 communicating said first circuit 22 and a discharge passage 11 of said primary hydraulic pump 10, a pressure accumulator 27 provided in said second circuit 25, a reproduction valve 30 switching said third circuit between a state permitting the flow of a pressurized fluid and a state blocking the flow, a pressure accumulation valve 26 provided for establishing and blocking communication of said second circuit 25, and a sequence valve 28 provided between said second circuit 25 on the side of said second pump motor 17 of said pressure accumulation valve 26 and the discharge passage 11 of the primary hydraulic pump 10.
According to the fourth invention, after accumulation of the pressurized fluid of high pressure in the pressure accumulator 27, the recovery valve 23 is placed in the second condition (closed), the pressure accumulation valve 26 is in communicating state and the reproduction valve 30 is in the first state (open), and in conjunction therewith, the set pressure of the sequence valve 28 is set by high pressure, the accumulated pressured fluid of high pressure can be supplied to the discharge passage 11 of the primary hydraulic pump 10 from the third circuit 29 via the pressure converter 18.
On the other hand, by placing the recovery valve 23 and the reproduction valve 30 at the second condition (closed) and the pressure accumulation valve 26 in communicating condition, and in conjunction therewith, by setting the sequence valve 28 at low pressure, the accumulated pressurized fluid of high pressure can be supplied to the discharge passage 11 of the primary hydraulic pump 10 via the sequence valve 28.
Thus, by driving the pressure converter 18 with the pressurized fluid of high pressure accumulated in the pressure accumulator 27, the pressured fluid of low pressure and large flow rate can be supplied to the discharge passage 11.
As set forth above, the pressurized fluid of pressure and high flow rate can be supplied to the discharge passage 11 by the pressurized fluid of high pressure accumulated in the pressure accumulator 27, and whereby driving the pressure converter 18. Also, the pressurized fluid of high pressure accumulated in the pressure accumulator can be supplied to the discharge passage 11 via the sequence valve 28.
While the actuator is in actuated state, by placing the recovery valve at the first condition (open), the pressure accumulation valve 26 at the closed position, the reproduction valve 30 at the second position (closed), and further setting the set pressure of the sequence valve 28 at low pressure, the returning pressurized fluid of the first circuit 22 can be supplied via the pressure converter 18 and the sequence valve 28.
On the other hand, by placing the recovery valve 23 and the reproduction valve 30 at the first position (open) and the pressure accumulation valve 26 at a closed position, and further setting the set pressure of the sequence valve 28 at high pressure, the returning pressurized fluid of the first circuit 22 can be supplied to the discharge passage 11 through the third circuit.
As set forth above, the returning pressurized fluid from the actuator can be supplied to the discharge passage with elevating the pressure converter 18 without accumulating the pressure of the pressurized fluid, and also, the returning pressurized fluid can be efficiently supplied to the discharge passage 11 via the third circuit 29 without accumulating the pressure of the pressurized fluid.
The fifth invention is a pressurized fluid recovery/reutilization system as set forth in claim 4, which includes first means for detecting a discharge pressure P2 of said primary hydraulic pump 10, a second means for detecting an accumulated pressure P1 of said pressure accumulator 27 of said second circuit 25, and third means for switching said recovery valve 23, said pressure accumulation valve 26 and said reproduction valve 30 on the basis of detected pressures of said first and second means, and in conjunction therewith to vary the set pressure of said sequence valve 28, said third means has a function for placing said recovery valve 23 at said second state, said pressure accumulation valve 26 in a communicating condition and said reproduction valve 30 in the first condition and in conjunction therewith setting the set pressure of said sequence valve 28 at high pressure when a differential pressure of said accumulated pressure P1 and the discharge pressure P2 is higher than or equal to a set differential pressure, and placing said recovery valve 23 and said reproduction valve 30 at said second state and said pressure accumulation valve 26 at the communicating condition and in conjunction therewith setting the set pressure of said sequence valve 28 at low pressure when the differential pressure of said accumulated pressure P1 and the discharge pressure P2 is lower than or equal to said set differential pressure.
By the fifth invention, when the differential pressure of the accumulated pressure P1 and the discharge pressure P2 is higher than or equal to the set pressure, the recovery valve 23 is placed at the second position (closed), the pressure accumulation valve 26 is placed at communicating position, the reproduction valve 30 is placed at the first position (open), and the set pressure of the sequence valve 28 is set at high pressure. Thus, the accumulated pressurized fluid of high pressure is supplied to the discharge passage 11 of the primary hydraulic pump 10 from the third circuit 29 via the pressure converter 18.
On the other hand, when the differential pressure between the accumulated pressure P1 and the discharge pressure P2 is less than or equal to the set differential pressure, the recovery valve 23 and the reproduction valve 30 are placed at the second position (closed), the pressure accumulation valve 26 is placed in a communicating position, and the set pressure of the sequence valve 28 is set at low pressure. Thus, the accumulated pressurized fluid of high pressure is efficiently supplied to the discharge passage 11 of the primary hydraulic pump 10 via the sequence valve 28.
As set forth above, since the accumulated pressurized fluid of high pressure can be supplied selectively via the pressure converter 18 or via the sequence valve 28 depending upon the differential pressure between the accumulated pressure P1 and the discharge pressure P2, the accumulated pressurized fluid of high pressure can be efficiently supplied to discharge passage 11 for effective use.
The sixth invention is a pressurized fluid recovery/reutilization system including first means for detecting a discharge pressure P2 of said primary hydraulic pump 10, a third means for detecting the pressure P3 of a returning pressurized fluid of said first circuit 22, and third means for switching said recovery valve 23, said pressure accumulation valve 26 and said reproduction valve 30 on the basis of detected pressures of said first and third means, and in conjunction therewith to vary the set pressure of said sequence valve 28, said third means has a function for placing said recovery valve 23 at said first state, said pressure accumulation valve 26 in a blocking condition and said reproduction valve 30 in the second condition and in conjunction therewith setting the set pressure of said sequence valve 28 at low pressure when said pressure P3 is lower than said discharge pressure P2, and placing said recovery valve 23 and said reproduction valve 30 at said first state and said pressure accumulation valve 26 at the blocking condition and in conjunction therewith setting the set pressure of said sequence valve 28 at high pressure when said pressure P3 is higher than said discharge pressure P2.
By the sixth invention, when the pressure P3 of the returning pressurized fluid is lower than the discharge pressure P2, the recovery valve 23 is placed at the first position (open), the pressure accumulation valve 26 is placed at blocking position, the reproduction valve 30 is replaced at the second position (closed) and the set pressure of the sequence valve 28 is set at low pressure. Thus, the returning pressurized fluid of the first circuit 22 is supplied to the discharge passage 11 via the pressure converter 18 and the sequence valve 28.
On the other hand, when the pressure P3 of the returning pressurized fluid is higher than the discharge pressure P2, the recovery valve 23 and the reproduction valve 30 are placed at the first position (open), the pressure accumulation valve 26 is placed at blocking position, and the set pressure of the sequence valve 28 is set at high pressure. Thus, the returning pressurized fluid of the first valve 22 is supplied to the discharge passage 11 through the third circuit 29.
As set forth above, when the pressure of the returning pressurized fluid is lower than the discharge pressure, the returning pressurized fluid from the actuator can be supplied to the discharge passage with elevating the pressure by the pressure converter 18 with accumulation of the returning pressurized fluid, and when the pressure of the returning pressurized fluid is higher than the discharge pressure, the returning pressurized fluid can be efficiently supplied to the discharge passage 11 via the third circuit 29 without accumulation of the returning pressurized fluid.